How do I add lots of holes into the surface of my model?
If the drill hole plans are in vector already convert the file to .svg.

If the hole plans are not vector.
Convert the holes to vector using Inkscape, Illustrator, etc...
Once everything is traced/converted save this file as .svg.

When you have a usable .svg file.
Open Blender and choose File/Import/Paths
Choose your .svg
With the newly created path selected in blender.
Go to the curve options and raise the extrude value up.
If the alignment is good, use the boolean modifier to "cut" the holes. Example

If not already vector &amp; automated methods fail. Instead of manually tracing the holes. You may be best off duplicating a cylinder, of the correct size, &amp; placing the duplicates where need be. Using the mirror modifier if and/or where possible. Then use the boolean modifier as mentioned previously.